The present invention relates to a rear-end spoiler for a full-rear vehicle.
Full-rear vehicles have a rear-end angle of slope ν>30° according tp the textbook “Aerodynamik des Automobils” [Aerodynamics of the Automobile] by Wolf-Heinrich Hucho (1st edition, 1981), page 183.
Experiments have shown that unstable fluid conditions prevail at rear-end angles of slope between 30° and 40° in the rear-end area of the motor vehicle. At a rear-end angle of slope of ν<30°, the flow breaks away at the rear edge of the roof with a clearly defined and thus a relatively small vortex wake. At a rear-end angle of slope ν>40°, the flow separates at the lower edge of the rear-end slope, accompanied by powerful lateral boundary vortices, which significantly increase the vortex wake and thus greatly increase the aerodynamic forces (resistance and lift). For this reason, the angle of slope range of 30° to 40° was avoided for many years until sport utility vehicles in particular discovered this angle of slope range as the “in” style. As a remedy for aerodynamic problems with “modern” rear-end angles of slope, roof spoilers have been successful in general with such vehicles. For the flow, this results in a rear-end angle of slope that is smaller than optically perceptible. This full-rear roof spoiler thus constitutes an extension of the roof and basically has a lower potential for reducing rear-axle lift. Roof spoilers thus differs from conventional spoilers which generate additional potential for lift reduction with a flow deflection, but in doing so also increase air resistance and therefore have only limited aerodynamic efficiency.
In known full-rear vehicles (e.g., the BMW X5), a roof spoiler aligned with the top of the roof may be arranged in the area of the rear edge of the roof above the rear window, so the rear-end separation edge of the airflow is shifted toward the rear and thus the dead zone behind the vehicle is reduced. The roof spoiler reduces aerodynamic lift on the rear axle and improves air resistance. Because the longitudinal extent of a roof spoiler must be limited for visual reasons, the aerodynamic effect of such a roof spoiler is limited.